Telephone-exchange system.



PATENTED SEPT. 24, 19w.

E. E. CLEMENT. TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED DEO.10. 1904.

mvenboc wit" use UNITED STATES PATENT OFFICE.

TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented Sept. 24, 1907.

7 Application filed December 10,1904. Serial No. 236,282-

To all whom it may concern.-

lie it known that l', EnwAnn E. CLEMENT, a citizen of the United States, residing at Washington, District of (olumbi-a. have invented certain new and useful Improvements in Telephone-Exchange Systems, of which the following is a specification, reference being had therein to the accompanying drawing[ My invention relates to telephone systems, and has for its object to provide a line signal circuit for exchange systems wherein perfect balance, simplicity, and cer-. tainty of operation will be combined, wherein also the line and talking circuit will be disengaged entirely from the battery circuit except through the cord circuit, (luring connection thereof.

Briefly stated. my invention comprises a line connected normally to the line lamp or signal relay through I the. normally closed contactsot' a cut-off relay, the cutoff relay being normally disconnected but adapted to be brought into connection with the line when the lamp or signal relay is actuated. After once coming into con nection with the line, the cut-off relay maintains its own connection. and also cuts off the line relay, which then becomes inert and remains so until the lines are again disconnected at the conclusion of the conversa tion by the withdrawal of the plugs.

My invention is illustrated in the accompanying drawing, in which the figure is a diagram showing two subscribers stations connected to an exchange, and the connecting cord circuit at the latter.

In the drawing, A and A are the subscribers stations, each equipped with the apparatus usual in common battery exchange systems, here typified only by the re ceiver R the transmitter T, ringer Q, and the switchhook S. From each station line wires 12 lead to the central ofiice, terminating at the jacks .I and J of a switchboard. Beyond the jacks each line has extensions passing to the armatures 1n and m of the cut-off relay M, and to the armatures l and Z of the line or signal relay L. The latter has its windings" divided, as indicated at l and l, the line connection passing from armatures of magnet M by way of the wires 5 and 6, when those armatures are retracted, to the windings l and l and then by wires 7 and 8 to the bus bars 18 and 19 of the main battery B. The magnet M is normally disconnected, but when the line relay L attracts its armatures magnet M is bridged across the line by way of the wires 3 and 4 and the front contacts of relay L. Also, when the armatur es m and m of magnet M are attracted they themselves connect the magnet in bridge relation to theline through direct connection with their front contacts; The relay L controls the local circuit 9 10- 11 of the signal lamp L, which I haveshown connected through front contacts of the relay L and back contacts of the relay M, for a purpose I shall reier to in the statement of operation. With this line circuit any standard common battery cord circuit may be employed, and I have shown a simple metallic circuit, 1213, 1415, with condensers C, so as to enable divided supervision, and low wound impedance coils I, I, which may or may not be the supervisory relays. The magnets L and M are preferably not of very low resistance, the actual resistance in practice varying according to the voltage and the line resistances. I do not limit myself to any specific resistance of either, but merely state that with a line resistance not exceeding 100 ohms, and a battery voltage of 25, the cord coils may be from 50 to 100 each, and the magnets L and M from 250 to 350 each.

sistance for the shunting effect to which reference will be made, to be realized.

The operation-oi my system is as follows: The parts are normally in the position shown in the drawing. When a subscriber calls, as A, he closes the line circuit and current flows therein from battery B through the windings l and l of relay L, which attracts its armatures and not only connects the relay Min circuit, but also closes the circuit of the lamp L, which glows. The current flowing to line from battery B at this time will not energize relay M sufficiently to pull up its arniatrues, and this may be made the more certain by making them with limited to that passed by the resistance of relay L, this result is capable of certain ascertainment. When the operator perceives the signal, she inserts the answering plug P into jack J, and listens and rings in the usual way, after testing the wanted line jack and fully inserting therein the mate plug P. All the subsidiary apparatus for these successive operations or steps I have omitted as forming no part of my invention and not being essential to this disclosure. They may all be standard or usual, and the cord may be'connected in any desired way so long as the battery is bridged. Evenhere' there may be a variation if the line conditions are changed. The battery may begrounded if the relays L and M arejlikewise grounded. When the battery B is connected through the cord and its coils I and I" to the line, current through relay L is checked by the counter E. M. F. presented, and an increase of current is produced in coil M sufiicient to operatively energize this relay and pull up its armatures to'disconnect the relay L. In order that this relay L may not by releasing its armatures disconnect the relay M before the latter has pulled up and closed its own circuit, I make the wide air gaps or otherwise to require a strong pull." The relay being shifiited by the line and the current They should be sufficiently higher than the line in rearmatures l and l" somewhat sluggish in their action.

After armatv'resn and m are once pulled up they stay up as long as the plug P is in the jack J, and wires 3, 4, 5 and 6 are all open, the former at contacts of armatures l and l, and the latter at armatures m and m. Thus the magnet M alone is bridged, and the only battery connection is that through the cord. The impedance of the coil M is of course made suflicient to prevent shunting of voice currents.

The above is the operation for a calling line. When a line is called by using plug P the operation is slightly different. The insertion of the plug will not cause relay M to pull up because that relay is stil disconnected. Neither will it cause relay L to pull up because the difference of potential at its terminals is balanced or zero. When the called subscriber answers, however, relay L pulls up, but the instant it does the relay) also pulls up, as the plug is already in, and the lamp 1/ does not glow because its circuit is broken practically at the same instant it is made. In order to guard against the effects of any slowness in the retraction of the armatures of relay L, however, I preferably provide a pair of back contacts on the relay M- which are included in the local circuit 9l0l 1. of lamp L, sothat relay M not only cuts offrelay L, but incidentally and instantaneously hmksthe lamp circuit.

Many changes can be made in this circuit by grounding, or by differently connecting the interlocking relays L and M. I contemplateall these changes, however, as within the scope of my invention, and desire the same clearly understood. For a two-Wire multiple circuit this is clear of many objections ordinarily raised, since the cutoff relay is normally out of circuit entirely, and the line relay takes the entire current in the line.

The arrangement shown may be applied to trunk lines as well as subscribers lines, and in other places. The relay L may be asignal magnet instead of a relay.

Having thus described my invention, what I claim is: 1. In a telephone system, a line, a line relay, a cut-off relay, and means whereby each relay controls the operative connection of the other. v

2. In a telephone exchange system, a signal magnet and a controlling magnet therefor, means controlled by the signal magnet to'put the controlling magnet in operative condition, means controlled by the controlling magnet to disable the signal magnet, and furthermeans controlled respectively from two points on a line to direct these operations.

3. In a common battery telephone exchange system, a line circuit, a signal, relay normally connected to the line. a battery connected to furnish current to line through the relay, a cut-0Ev relay controlling the connection of the signal relay, means controlled by the signal relay to connect the cut-off relay, and further means becoming opetative on making connection with the line to energize the cutoff relay when-connected.

4. In a common my telephone exchange system, a

'subscribers line, a cut-bl! relay and a line signal relay having their armature coiitncts connectedin parallel to Hie, cooperating contacts of the cut-oft relay in circuit with the winding of the'signal relay, contacts of both relays in circuit with the winding of the cut-off relay, and means controlled by an operator in making connection with the line to direct operating current through the cutoff relay.

5. In a telephone exchange system, a subscribers line.

a battery and signal magnet normally in series therewith,

a cut-ofl' relay therefor controlling said series connection and adopted to become connected in a bridge of the line when the signal magnet is actuated, an operators cord circuit adapted for connection with the line, and battery .connections for said cord circuit such that upon making EDWARD E. CLEMENT.

Witnesses THOMAS DURANT, EDWARD F. COLLADAY. 

